Limited-colour screens could boost cellphone battery life

点击量： 时间：2019-03-08 11:07:00

By MacGregor Campbell (Image: Johnson Chuang) (Image: Johnson Chuang) (Image: Johnson Chuang) Flat-panel displays based on organic LEDs are tipped to replace the now-ubiquitous LCD panels, thanks to a host of benefits including greater energy efficiency. Now researchers have shown that OLEDs can be made even more frugal by carefully choosing the balance of colours used to make up an image. Each pixel in an OLED screen is made from a spot of polymer that emits coloured light when supplied with power, and each uses different amounts of energy depending on the colour being displayed. At the same brightness, yellow, for example, uses less energy than magenta. “Colours with equal perceived brightness don’t necessarily use the same amount of energy,” says Johnson Chuang of Simon Fraser University in British Columbia, Canada, who led the study. LCD panels, by contrast, use the same amount of energy no matter what hue the screen, because the backlights in the display always remain switched on. By using this quirk of the newer technology, Chuang and his colleagues were able to design sets of colours that slash the power consumption of an OLED panel by up to 40 per cent, with minimal effect on how people perceive an image The researchers ranked the expected power consumption of all the colours that make up the standard CIELAB colour space used to build display hardware. They then chose a subset that requires much less power than the full colour space, but still makes it possible to distinguish the features of a scene. The colour choice resulted in energy savings of between 37 and 41 per cent over a traditional colour palette, depending on the scene being shown. The new colour palette could help the designers of mobile devices like cellphones extend their battery life. Today, about half the stored power of a mobile device like a phone is typically used to run its LCD display. “Say you’re running low on battery and you want to use Google maps to get home,” says Chuang. “Switching to an energy-aware colour set could make your battery last longer.” “It could potentially be useful for mobile devices,” says David Borland, a data visualization researcher at the University of North Carolina, who was not involved with the project. However, Borland points out that these energy-aware colour sets have only been described for discrete colours at this stage, reds and greens, for example, and can’t portray the entire range of shades between two colours. Chuang acknowledges that means some details can become indistinct, as this image illustrates. Chuang now plans to start testing how much energy the new colour palettes can save on physical devices. He says that the energy savings will depend on the specific display, the content, and user preference, but should be significant over OLED displays that use a full colour set. “It depends on how much the user wants to sacrifice,” says Chuang. More on these topics: